#define  _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdbool.h>
typedef struct ListNode ListNode;
struct ListNode
{
    int val;
    struct ListNode* next;
};
typedef struct ListNode ListNode;
bool hasCycle(struct ListNode* head)
{
    ListNode* slow = head;
    ListNode* fast = head;
    while (fast && fast->next)
    {
        slow = slow->next;
        fast = fast->next->next;
        if (slow == fast)
        {
            return true;
        }
    }
    return false;
}